Block 2 - Microbial Genetics Flashcards by Matthew Obernuefemann

The entire complement of genes of all chromosomes.

Genome

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What is the transfer of DNA from donor bacterium to recipient bacterium by using a bacterial virus as the vehicle?

Transduction

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Which genes direct the synthesis of proteins with related functions and which are regulated as a “unit”?

genes of the operon

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True or False:

The new double-stranded DNA re-winds into a helix as the parental DNA unwinds exposing more nucleotides to be replicated.

True

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Describe “semiconservative replication”.

When the entire chromosome is copied, each double helix consists of one newly synthesized strand of DNA bound to one original parent strand

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One entire double-strand of DNA containing multiple genes

[is always DNA, except in RNA viruses.]

Chromosome

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This enzyme binds to DNA and inserts complementary nucleotides thereby generating a new strand.

DNA polymerase

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What is the result of a frameshift mutation?

A frameshift mutation usually results in missense mutation or in a significantly different, nonfunctional or incomplete protein.

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True or False:

The replication of the lagging strand is continuous because of this process of producing short fragments and joining them to the existing strand.

A new fragment is generated each time the replication fork advances a short distance. This process continues throughout the entire replication process until the entire DNA has been replicated.

False

The replication of the lagging strand is discontinous; not continuous.

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What is the term for the strand that has the 5’ end of the exposed nucleotide facing toward the replication fork?

In which direction does the newly developing strand grow with regards to the replication fork? Toward the fork or away from the fork?

The “lagging” strand

Grows away from the fork

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What are the two types of operon?

inducible and repressible

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What assists protein synthesis by serving as a “facilitator” for the mRNA and tRNA functions?

rRNA, “ribosomal RNA”

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In DNA, what are the “long chains” of nucleotides?

What does the term “antiparallel” refer to?

strand

The two strands run in opposite directions; i.e. the nucleotide of the 3’ end of one strand pairs up with the nucleotide of the 5’ end of the adjacent strand. Strands are not identical, but are complementary.

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What are the genes that are expressed only when certain environmental conditions are present?

(e.g. genes for enzymes of a biosynthetic pathway are expressed only when the appropriate substrate is present, i.e. presence of substrate causes Operator site to be unblocked.)

inducible genes

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The mRNA “docks” into what portion of the ribosome?

“into the groove”

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When does transcription end?

Transcription ends when the RNA polymerase reaches the termination region of the gene, and the new single-stranded mRNA is released (the DNA re-winds).

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Within the operon,

What is the site of the chromosome which controls, by either permitting or blocking, the access of RNA polymerase to the structural genes of the operon site to which the repressor protein binds (or fails to bind)?

operator site

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What is the term for the direct uptake of DNA segment from one bacterium to another as “naked” DNA in solution?

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transformation

What is the integration of the DNA of a temperate bacteriophage (virus) into the bacterial chromosome where it replicates along with the bacterial chromosome?

What is produced upon separation from the bacterial DNA?

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Lysogeny

produces a new bacteriophage

What carries the genetic code from the DNA to the ribosome?

In mRNA, 3 nucleotides = 1 _________.

1 _________ = 1 amino acid

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mRNA (messenger RNA)

codon

In regulation of gene expression,

The genes that are constantly expressed (transcribed and translated into functional products) (60-80% of genes are in this category) are considered to be what type of gene?

These genes can be “turned on”

These genes – can be “turned off”

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constituitive genes

inducible

repressible

What molecules make up a nucleotide (3 parts)?

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) 5-carbon sugar: ribose / deoxyribose
) nitrogenous base: bound to the first or 1’ (one prime) carbon position of the 5 carbon sugar

Purines:
Adenine
Guanine
Pyrimidine:
Thymine
Cytosine
Uracil (only in RNA)

3.) Phosphate Group - bound to the fifth or 5’ carbon of the sugar molecule

What is the transfer of the genetic code on DNA gene into a messenger RNA (mRNA) strand by means of DNA-dependent RNA polymerase?

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transcription

What are related genes that are regulated as a group/series?

Within the above system:

What is the type of gene that codes for a “repressor” protein which can bind to the “operator” region of the operon?

What is the region of the chromosome to which the RNA polymerase binds during transcription?

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Operon

“repressor gene”

promoter site

What is the result of "recombination" in gene segments?

It can result in major changes or a non-functional cell.

Where does the RNA polymerase bind to DNA during transcription?

at the promoter site (beginning of the gene)

What is the small, circular, self-replicating piece of the DNA that is **separate** from the normal chromosomal DNA *in bacteria*?

the plasmid

What is the synthesis of a polypeptide at the ribosome through linkage of amino acids in a sequence specified by a mRNA molecule?

translation

What is the transfer of the genetic code on DNA gene into a messenger RNA (mRNA) strand by means of DNA-dependent RNA polymerase? What is the synthesis of a polypeptide at the ribosome through linkage of amino acids in a sequence specified by a mRNA molecule?

transcription translation

True or False: The anticodon is a part of the tRNA; the codon is a part of the mRNA.

True

What three types of base substitution mutations can occur?

1. **silent**: *no change in the protein* 2. **missense**: *different amino acid in the protein*; usually not highly significant 3. **nonsense**: RNA polymerase is stopped from reading the code resulting in an *incomplete, nonfunctional protein*

Genetic mutations, at the cellular/molecular level, are typically caused by what three things?

spontaneous mutation chemical mutagens radiation

A segment of DNA that contains the genetic code (blueprint) for a functional product.

Gene

In DNA replication: Replication forks form where short lengths of double-stranded DNA helix unwind, thus exposing the separated strands. **Unwinding (and rewinding) is due to action of what enzymes?** These enzyme break the hydrogen bonds between bases and/or hold part of the strand stable.

helicase DNA gyrase topoisomerase

What is the transfer of genetic material between donor and recipient cells involving direct **cell-to-cell contact**? What structure is used to transfer DNA from one cell to another in this form of genetic material transfer?

Conjugation Sex pilus

Nucleotides are always added to which exposed end of the helix? What is the term for the strand that is the newly growing strand?

3'; thus growing from 5' to 3'-extending at the 3' end "leading" strand “Leading” strand is the newly growing strand having the 3’ end of the exposed nucleotide “facing toward” (“leading into”) the replication fork (a) The newly developing strand grows toward the replication fork, i.e. “leads into” the fork (b) The strand is continuously replicated because of enzymatic simplicity and ease of access to the molecule

What is the definition of the changes (substitutions or deletions) in the sequence of DNA bases, thus changing the genetic code? What are the two types?

genetic mutation base substitution frameshift mutation

This enzyme facilitates linkage of a nucleotide to both 3’ and 5’ binding sites simultaneously and inserts a nucleotide to join the newly replicated fragment with the existing strand.

DNA ligase

In/on the ribosome, the "50S" portion and the "30S" portion are located on what part of the ribosome, respectively?

50S = top (above the groove) 30S = bottom (below the groove)

What is needed to initiate strand growth in the absence of a nucleotide having a 3’ binding site? The RNA primer provides what site?

RNA primer and RNA polymerase a 3' site

What molecule transports and then transfers the amino acid to the developing peptide chain? What is the site **on** the tRNA that **bonds** with the codon on the mRNA (carries the three bases which complement the codon)? This specifies which amino acid will be carried by the tRNA.

tRNA (transfer) anticodon

**What are the terms for each definitions regarding types of mutations:** A single base is replaced with another, thus changing the codon. May result in an improper amino acid in the protein. Insertion or deletion of bases may shift the codon reading frame of the mRNA in the ribosome.

base substitution frameshift mutation

The total genetic makeup of an organism. The expressed properties of an organism.

Genotype phenotype

What are the genes that are expressed **except** when certain environmental conditions are present? (e.g. presence of certain metabolic products causes genes for metabolic enzymes to be repressed, thus slowing down metabolism, i.e. presence of metabolic products causes Operator site to be blocked.)

repressible genes

Block 2 - Microbial Genetics Flashcards

(44 cards)